In this book I have discussed several practical issues revolving around the concept of personhood. My intention has been to show that, with a clearer understanding of what a person is, we can illuminate — and in some cases even answer — some critical questions of practical ethics. I have also tried to demonstrate not merely the relevance but the vital importance of ethical theory to our efforts to settle morally complex issues.

I began with the assumption that a person is any individual who is entitled to being treated in accordance with all sound moral principles. We may then decide who counts as a person by determining first what basic moral principles are sound, and then what characteristics make it right and reasonable to treat someone in accordance with them. I argued that there are two fundamental principles — beneficence and fairness - which are acknowledged in virtually all moral systems. Together these would, if followed consistently, lead us toward what appears to be the central, overall purpose for having moral rules and practices: namely, bringing about the greatest happiness for everyone which is consistent with a like happiness for all other persons.

Beneficence, which enjoins us to make individuals happy and remove or prevent unhappiness, can apply only to those capable of happiness or unhappiness: i.e., conscious beings. Any individual which is aware of and cares about what happens to it can profit from being treated in accordance with beneficence. So there is a point to applying that principle to any sentient being; moreover, I argue that we not only can but ought to treat all sentient beings beneficently.

Fairness is treating everyone's interests on an equal basis. This amounts to not letting any one individual benefit at another's expense. Person A benefits at B's expense when, through obtaining that benefit, A prevents B from attaining a level of happiness comparable to A's. Only those who have the capacity of acting fairly are, I tried to show, clearly entitled to being treated fairly. If those who can consider the interests of everyone were to treat all non-rational individuals with the same concernthey give the rational, rational individuals will lose and the non-rational will benefit at the expense of the rational. Not only would the rational get nothing back for their pains, but the costs would be incalculable, given that non-rational creatures vastly outnumber us.

I call those who are both sentient and rational natural persons, for they have characteristics that make it right and reasonable to treat them with both beneficence and fairness. Although we cannot, without being unfair to ourselves, treat all non-rational creatures with fairness, we can treat any that are sentient with beneficence. And we should, to the extent that we can do so without harming or seriously depriving rational individuals. In addition, we ought to extend personhood to some types of non-rational individuals, if doing so will bring benefits to rational people generally. Extending personhood requires protecting the interests of individuals who are, primarily because of failure of rationality, unable to protect their own interests. The practices and institutions which protect the interests of the helpless are valuable for anyone who might become helpless himself. This includes all of us, of course, for we all begin life helpless and never know when we might become helpless again. Probably the most important of all such practices is that anyone who is a person will not cease to be treated as a person so long as how he is treated can matter to him. Losing personal status is serious not only because it can result in loss of tangible goods, but because any loss is worse than never having something in the first place.

With this background I draw a number of conclusions:

Non-rational Humans. Infants and small children, as well as those are mentally incompetent as a result of developmental disabilities, in illness, brain damage, or senility, vary greatly in their capacity to understand what is going on around them and appreciate their interests and those of others. Some do not care what is done to them; others care deeply, and many vary with time and circumstances in what they are able to assimilate. For this reason it is not possible to draw lines between rational and non-rational humans. Furthermore, no one knows what may happen to herself or those she loves, so that we all have a strong interest in protecting the rights and interests of all people we care about. We cannot, however, expect others to protect and not exploit us if we do not do the same for others by supporting practices and institutions that foster caring for the helpless. We all have an interest in extending personhood to children and the mentally disabled and seeing to it that their personhood is not revoked when it becomes inconvenient. These individuals ought to be treated not only with beneficence but also with fairness, and no group of such extended persons ought to have personhood taken away from it.

Animals. Any animal which demonstrates rational activity, especially one which can universalize, understand the consequences of its actions, and put itself imaginatively in the place of others is a natural person and we should not exploit such animals, if there are any, for our own profit and pleasure. For any animal which we have absolutely no reason to believe can feel pain, it does not matter how we treat it. We should avoid harming sentient but non-rational animals, but we do not have to consider their interests equally with those of humans. We may, when it will benefit humans significantly, and there is no other way to obtain those benefits, sacrifice their interests to our own. If we can change our lives in ways that bring us only minor inconveniences, but which avoid causing suffering to animals, we should.

Future People. Those who will live in the future have no interests now that we can or need consider, but when they live, they will have interests. These interests will often be affected significantly by what we do today. These interests, like the interests of people who live far from us in space, should be given equal weight with our own in the sense that we ought not to promote our own interests in ways that we can be reasonably certain will be destructive of theirs. Those who will never exist will never have any interests, and no one will be wronged if we act in ways which would harm individuals if they were to exist, but who never do. In particular, we have no duty to future people to bring them into the world; we ought not, however, to bring people into the world when we believe them to have no reasonable prospects of happiness.

The Human Fetus1. Fetuses2 which are non-sentient, like non-sentient animals and humans who will exist only in the future, have no present interests. If they are allowed to develop, they will be sentient and will have interests. If a fetus3 is destroyed before it becomes sentient, no harm or wrong is done to it, and decisions to abort4 or use fetal tissue at this time need consider only the interests of existing persons. No woman should be forced to bear a child against her will, and early abortions5 at least ought to be freely available. On the other hand, if a fetus6 is allowed to develop, its future interests as a person must be given full consideration. Caring for a fetus7 which will become a person is primarily its mother's responsibility, but the burden should be shared by its father and others in society. Fetuses8 which could be sentient also have some interests, and pain should not be inflicted upon them unnecessarily. We could extend personhood to them if we wished, and we ought to do so if those who are already persons will benefit. At the present time I do not believe that present persons stand to benefit from extending personhood to any fetuses9. Too many infants, children, and adults are deprived of basic goods for us to be expending resources on the unborn apart from what is needed to give them a good start in life if they are born. I conclude that we are justified in allowing abortion10 of sentient fetuses11 when this is necessary for protecting significant interests of persons.

Death. I agree with those who think that it is reasonable to define death as a state in which the individual neither has nor can have further interests. At the present time, brain death12 is generally recognized as such a state. But there are individuals who are known with virtual certainty to be permanently unconscious, but whose brains have some minimal activity. There would be many advantages to counting such individuals as dead in the personal (as opposed to the biological) sense — i.e., as no longer persons — and no harm could be done to them by ceasing to give them moral consideration. Among these advantages would be allowing their organs to be used in transplants13 and, more important, freeing medical resources for those who have a chance at meaningful life.

Cessation of Medical Treatment and Euthanasia. Many individuals who still have interests may have those interests best served by being allowed to die, or even assisted in hastening their deaths. I argue that medical professionals should be permitted to cease life-saving treatments, and even to perform euthanasia, under certain circumstances. With regard to euthanasia, the most important caveat is to prevent possible abuse by those who would profit from the death of another. It seems to me that strict safeguards against abuse are feasible. In considering whether to stop medical treatments, the main consideration should be the patient's best interest. Yet some therapies are so costly that even if they have a chance of doing some minimal good to a patient, providing them may not be justified if this would deprive others of significant medical — or other — goods. In general, all human beings between birth and death are persons and their interests need to be considered equally.

I have concentrated only on those issues that are directly related to the concept of personhood. There are, of course, countless other practical questions which I did not address. For example, I have not touched on the issue of informed consent or the implications of genetic research. I have not discussed beyond some general principles what sort of distribution of resources among nations, with future generations, or even within a given society, would be most just. Nor have I said in great detail how we ought to change the way we treat animals. There is room for much work in discussing these issues, and I think that the general notions implicit in my basic theory would prove helpful in doing so. In addition, scientific research dealing with the mental capacities of fetuses14 and animals and with the environmental effects of population trends and various ways of managing natural resources will contribute immeasurably to finding answers to questions raised here.